Résumé

Mineral carbonation of serpentinite mining residue offers an environmentally secure and permanent storage of carbon dioxide. The strategy of using readily available mining residue for the direct treatment of flue gas could improve the energy demand and economics of CO₂ sequestration by avoiding the mineral extraction and separate CO₂ capture steps. The present is a laboratory scale study to assess the possibility of CO₂ fixation in serpentinite mining residues via direct gas-solid reaction. The degree of carbonation is measured both in the absence and presence of water vapor in a batch reactor. The gas used is a simulated gas mixture reproducing an average cement flue gas CO₂ composition of 18 vol.% CO₂. The reaction parameters considered are temperature, total gas pressure, time, and concentration of water vapor. In the absence of water vapor, the gas-solid carbonation of serpentinite mining residues is negligible, but the residues removed CO₂ from the feed gas possibly due to reversible adsorption. The presence of small amount of water vapor enhances the gas-solid carbonation, but the measured rates are too low for practical application. The maximum CO₂ fixation obtained is 0.07 g CO₂ when reacting 1 g of residue at 200 °C and 25 barg (pCO₂ ≈ 4.7) in a gas mixture containing 18 vol.% CO₂ and 10 vol.% water vapor in 1 h. The fixation is likely surface limited and restricted due to poor gas-solid interaction. It was identified that both the relative humidity and carbon dioxide-water vapor ratio have a role in CO₂ fixation regardless of the percentage of water vapor.